The present invention generally relates to a method and apparatus for providing reference laser beams and, more particularly, to such a method and apparatus in which two such beams simultaneously define a reference plane and a reference line spaced above and extending generally parallel to the plane.
Laser beam systems have been employed in numerous surveying and construction applications. In one such system disclosed in U.S. Pat. No. 4,062,634, issued Dec. 12, 1977 to Rando et al, and assigned to the assignee of the present invention, a laser beam projecting apparatus provides a rotating laser beam which establishes a reference plane. The rotating laser beam is used to provide a continuous, visible plane of light that creates a constant horizontal benchmark of elevation over an entire work area. Also, one or more laser beam detectors are placed at considerable distances from the projecting apparatus for intercepting the rotating laser beam and determining elevations of selected points throughout the work area.
In the laser beam projecting apparatus of the cited patent, the generally horizontal rotating reference laser beam is produced by projecting the beam generally upward and then deflecting it ninety degrees within a pentaprism or penta-mirror assembly. The pentaprism assembly is rotated about a vertical axis within the projecting apparatus to cause the horizontal beam to rotate and define the reference plane.
It is often desired to align the plane defined by a rotating reference beam in a generally perpendicular relationship with another building structure, for example such as a wall. The multiple reference beam apparatus of the above cross-referenced application has met this need, left unfulfilled by the Rando et al apparatus, by providing both a stationary reference beam and a rotating reference beam defining a plane which is normal to the stationary beam. The apparatus of the cited application employs a beam diverting assembly of optical elements which intercept and split a primary beam into partially transmitted and partially reflected portions. The reflected portion of the beam is diverted to a path which extends generally perpendicular to the path of the transmitted beam portion. By rotating the beam diverting assembly, the reflected and diverted beam portion is rotated about an axis defined by the transmitted beam portion, whereby both a stationary reference beam, and a rotating reference beam, defining a plane normal to the stationary beam, are produced.
For the most part, the overall performance and versatility of the above-described reference beam projecting apparatuses have met and even surpassed expectations. However, from time to time gaps in their capabilities are revealed when such apparatuses are tried in new applications not originally contemplated for them. It is, therefore, seen that a need exists for expansion of the capabilities of the beam projecting apparatus of the cross-referenced application to accommodate numerous other applications, such as are typically encountered in the surveying and construction fields.